Preparation And Characterization Of Nano-controlled Fluorescent Material Containing Yttrium

Rare-earth doped luminescent materials played an important role in phosphor,display, X ray, imaging, scintillation, lasers, batteries, biology and optical fibreamplifier fields. With the development of nanotechnology, low dimensionalnanomaterials usually exhibit novel optical, electronic, magnetic and mechanicalproperties. It is well known that the morphology, dimensionality, and size ofnanomaterials have tremendous effects on their properties. In this paper, a series ofyttrium-containing luminescence host materials were synthesized, such as NaY(MoO4)2,Y2O3and NaYF4nanocrystals. The luminescence properties as well as applications inthe field of batteries were investigated. The main contents in this thesis are as follows:1. NaY(MoO4)2is one of excellent laser host materials. The concentrationquenching effect of rare earth ions hardly occurs in NaY(MoO4)2due to its specialcrystal structure. NaY(MoO4)2microcrystals with different morphologies weresuccessfully synthesized by a simple hydrothermal method via varying the molar ratiosof Y(NO3)3/Na2MoO4and pH values of the resultant solutions. By doping with Er3+,Tm3+, and Eu3+ions, NaY(MoO4)2was demonstrated to be a good host material fordifferent rare earth ions.2. Y2O3has a fine chemical and photochemical stability. Ag–Y2O3:Eu3+compositenanotubes were successfully synthesized when Y2O3was combined with Ag. Theeffects of the Ag content on the photoluminescence properties of the Ag–Y2O3:Eu3+composite nanotubes were investigated in detail. Moreover, the surface-enhancedRaman scattering effect of the Ag aggregates was evaluated by using4-aminothiophenol as a Raman probe molecule.3. NaYF4is acknowledged as the most efficient upconversion host material atpresent. NaYF4:Yb3+/Er3+/Pb2+nanocrystals were prepared by a hydrothermal method.The simultaneous phase and size control of NaYF4:Yb3+/Er3+nanocrystals with tunableupconversion luminescence was successfully achieved by trodoping with Pb2+ions. Theintensity ratio of2H11/2/4S3/2→4I15/2to4F9/2→4I15/2increased with increasing Pb2+concentration. 4. NaYF4:Yb3+/Er3+microcrystals prepared by a hydrothermal method were chosento design TiO2-NaYF4:Yb3+/Er3+composite photoanodes of dye-sensitized solar cells.Er3+ion can emit visible light under495or980nm excitation, and then the visible lightcan be absorbed by dye N719to improve light harvesting and thereby the efficiency ofthe solar cell. The results of the electrochemical test indicated that the incorporation ofNaYF4microcrystal improved the sunlight harvesting, but went against the electrontransport in dye-sensitized solar cells.In order to further improve the electron transport ability of the composite cells,NaYF4:Yb3+/Er3+-graphene composites were added to the TiO2photoanodes ofdye-sensitized solar cells, which were prepared by growing NaYF4:Yb3+/Er3+nanoparticles in interlayers of expanded graphite, accompanied with the simultaneousexfoliation of expanded graphite under phlyvinylpyrrolidone-assisted hydrothermalconditions. The incorporation of NaYF4:Yb3+/Er3+-graphene composites not only canimprove the sunlight harvesting on the basis of the upconversion function of rare earthions, but also can enhance the electron transport ability. And thus, the efficiencies of thesolar cells were enhanced.5. Other rare earth phosphors were explored, such as KLa2Ti3O9.5:Er3+nanocrystal and KMgF3: Eu nanocubes. In addition, the luminescence properties andphotocatalytic activity were studied in detail.